Electric powered vehicles such as hybrid vehicles, electric vehicles and fuel cell vehicles that can travel by using electrical energy have been developed and put to practical use as environmentally-friendly vehicles. An electric powered vehicle is equipped with a motor for generating vehicle driving force and a power storage device for storing driving electric power of the motor.
In the hybrid vehicles, there has been proposed a configuration in which a power supply outside the vehicle (also referred to as “external power supply” hereinafter) is used to charge a vehicle-mounted power storage device. Therefore, it has been desired to increase the distance traveled by using electric power stored in the power storage device. It is to be noted that charging the vehicle-mounted power storage device by using the external power supply is also simply referred to as “external charging” in the following.
Japanese Patent Laying-Open No. 2008-109840 (PTL 1), for example, describes a power supply system having a plurality of power storage devices (batteries) connected in parallel. In the power supply system described in PTL 1, a voltage converting device (converter) serving as a charge/discharge adjustment mechanism is provided for each power storage device (battery). In contrast, Japanese Patent Laying-Open No. 2008-167620 (PTL 2) describes a power supply apparatus for a vehicle equipped with a main power storage device and a plurality of sub power storage devices, wherein a converter for the main power storage device and a converter shared by the plurality of sub power storage devices are provided. With such a configuration, the number of converters can be suppressed and the amount of energy that can be stored can be increased.
In particular, in the configuration described in PTL 2, one of the plurality of sub power storage devices is selectively connected to the converter, and the main power storage device and the selected sub power storage device supply driving electric power of the motor for driving the vehicle. In this power supply apparatus, electric power supply is controlled based on an SOC (State Of Charge) indicating the remaining capacity of the power storage device. Specifically, when the SOC of the sub power storage device in use decreases, a new sub power storage device is connected to the converter. By sequentially using the plurality of sub power storage devices, the distance traveled by using electrical energy stored in the vehicle (EV (Electric Vehicle) travel distance) can be increased.